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Trapped in the depths of Halley's Comet, the Futuremen battle fourth-dimensional monsters in a titanic struggle to save the system's solar energy

Here's a relevant excerpt:

"Look, Simon! The first slops that vanished did so near the orbit of Uranus. The next ones disappeared further Sunward. The location of disappearances has
steadily moved in a Sunward direction."
"That's true," the Brain admitted. "Does it mean anything?"
"I don't know," Curt muttered. "But Halley's Comet has also been steadily moving in a Sunward direction, during these vanishings." His eyes flashed.
"Simon, I know it sounds insane, but I think that Halley's Comet has something to do with this mystery!"

And:

"They were all drawn into the comet by a magnetic beam, the same as we," he declared. "Simon, that beam was deliberately projected to seize us!"
"Aye, lad," came the answer of the helpless Brain. "There's intelligence and menace inside Halley's comet."